This invention relates to a portable, preferably wrist-mounted, device for monitoring heartbeat or pulse rate. Various physical exercises, and in particular those such as jogging which are practiced by individuals having widely varying ages and fitness factors, are beneficial only if performed within the range of levels which are reflected by the desired pulse rate of a given individual. If the individual's pulse rate does not rise to a particular lower level, the exercise may be of little effect whereas the effects can be decidedly harmful if an upper level is exceeded.
Prior art devices exist which monitor the beat of the human heart such as the monitor disclosed in U.S. Pat. No. 3,742,937. However, in that particular case, a visible light pulse is produced for each heartbeat measured during a fifteen second interval. Thus, once the light begins flashing, the flashing will continue for fifteen seconds and the user of the monitor must count the flashes from the light and multiply by four to obtain his present heart rate in beats per minute. A readout is, of course, extremely inconvenient to obtain and is subject to error in that the user may either miscount the flashes of light or make a mistake in multiplying the number of flashes times four and, thus, may obtain the incorrect or inproper heart rate.